Delete unused TaskRunner abstraction.

webrtc/base/task.h

-/*
- *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree. An additional intellectual property rights grant can be found
- *  in the file PATENTS.  All contributing project authors may
- *  be found in the AUTHORS file in the root of the source tree.
- */
-
-#ifndef WEBRTC_BASE_TASK_H__
-#define WEBRTC_BASE_TASK_H__
-
-#include <stdint.h>
-
-#include <string>
-
-#include "webrtc/base/sigslot.h"
-#include "webrtc/base/taskparent.h"
-
-/////////////////////////////////////////////////////////////////////
-//
-// TASK
-//
-/////////////////////////////////////////////////////////////////////
-//
-// Task is a state machine infrastructure.  States are pushed forward by
-// pushing forwards a TaskRunner that holds on to all Tasks.  The purpose
-// of Task is threefold:
-//
-// (1) It manages ongoing work on the UI thread.  Multitasking without
-// threads, keeping it easy, keeping it real. :-)  It does this by
-// organizing a set of states for each task.  When you return from your
-// Process*() function, you return an integer for the next state.  You do
-// not go onto the next state yourself.  Every time you enter a state,
-// you check to see if you can do anything yet.  If not, you return
-// STATE_BLOCKED.  If you _could_ do anything, do not return
-// STATE_BLOCKED - even if you end up in the same state, return
-// STATE_mysamestate.  When you are done, return STATE_DONE and then the
-// task will self-delete sometime afterwards.
-//
-// (2) It helps you avoid all those reentrancy problems when you chain
-// too many triggers on one thread.  Basically if you want to tell a task
-// to process something for you, you feed your task some information and
-// then you Wake() it.  Don't tell it to process it right away.  If it
-// might be working on something as you send it information, you may want
-// to have a queue in the task.
-//
-// (3) Finally it helps manage parent tasks and children.  If a parent
-// task gets aborted, all the children tasks are too.  The nice thing
-// about this, for example, is if you have one parent task that
-// represents, say, and Xmpp connection, then you can spawn a whole bunch
-// of infinite lifetime child tasks and now worry about cleaning them up.
-//  When the parent task goes to STATE_DONE, the task engine will make
-// sure all those children are aborted and get deleted.
-//
-// Notice that Task has a few built-in states, e.g.,
-//
-// STATE_INIT - the task isn't running yet
-// STATE_START - the task is in its first state
-// STATE_RESPONSE - the task is in its second state
-// STATE_DONE - the task is done
-//
-// STATE_ERROR - indicates an error - we should audit the error code in
-// light of any usage of it to see if it should be improved.  When I
-// first put down the task stuff I didn't have a good sense of what was
-// needed for Abort and Error, and now the subclasses of Task will ground
-// the design in a stronger way.
-//
-// STATE_NEXT - the first undefined state number.  (like WM_USER) - you
-// can start defining more task states there.
-//
-// When you define more task states, just override Process(int state) and
-// add your own switch statement.  If you want to delegate to
-// Task::Process, you can effectively delegate to its switch statement.
-// No fancy method pointers or such - this is all just pretty low tech,
-// easy to debug, and fast.
-//
-// Also notice that Task has some primitive built-in timeout functionality.
-//
-// A timeout is defined as "the task stays in STATE_BLOCKED longer than
-// timeout_seconds_."
-//
-// Descendant classes can override this behavior by calling the
-// various protected methods to change the timeout behavior.  For
-// instance, a descendand might call SuspendTimeout() when it knows
-// that it isn't waiting for anything that might timeout, but isn't
-// yet in the STATE_DONE state.
-//
-
-namespace rtc {
-
-// Executes a sequence of steps
-class Task : public TaskParent {
- public:
-  Task(TaskParent *parent);
-  ~Task() override;
-
-  int32_t unique_id() { return unique_id_; }
-
-  void Start();
-  void Step();
-  int GetState() const { return state_; }
-  bool HasError() const { return (GetState() == STATE_ERROR); }
-  bool Blocked() const { return blocked_; }
-  bool IsDone() const { return done_; }
-  int64_t ElapsedTime();
-
-  // Called from outside to stop task without any more callbacks
-  void Abort(bool nowake = false);
-
-  bool TimedOut();
-
-  int64_t timeout_time() const { return timeout_time_; }
-  int timeout_seconds() const { return timeout_seconds_; }
-  void set_timeout_seconds(int timeout_seconds);
-
-  sigslot::signal0<> SignalTimeout;
-
-  // Called inside the task to signal that the task may be unblocked
-  void Wake();
-
- protected:
-
-  enum {
-    STATE_BLOCKED = -1,
-    STATE_INIT = 0,
-    STATE_START = 1,
-    STATE_DONE = 2,
-    STATE_ERROR = 3,
-    STATE_RESPONSE = 4,
-    STATE_NEXT = 5,  // Subclasses which need more states start here and higher
-  };
-
-  // Called inside to advise that the task should wake and signal an error
-  void Error();
-
-  int64_t CurrentTime();
-
-  virtual std::string GetStateName(int state) const;
-  virtual int Process(int state);
-  virtual void Stop();
-  virtual int ProcessStart() = 0;
-  virtual int ProcessResponse();
-
-  void ResetTimeout();
-  void ClearTimeout();
-
-  void SuspendTimeout();
-  void ResumeTimeout();
-
- protected:
-  virtual int OnTimeout();
-
- private:
-  void Done();
-
-  int state_;
-  bool blocked_;
-  bool done_;
-  bool aborted_;
-  bool busy_;
-  bool error_;
-  int64_t start_time_;
-  int64_t timeout_time_;
-  int timeout_seconds_;
-  bool timeout_suspended_;
-  int32_t unique_id_;
-
-  static int32_t unique_id_seed_;
-};
-
-}  // namespace rtc
-
-#endif  // WEBRTC_BASE_TASK_H__